Due to advances in technology and manufacturing of portable electrical equipments, rechargeable batteries are required. The quality of these equipments depends on some parameters such as: capacity, charging time and battery life of the battery applied in these devices. The charger technology depends on the technology and size of the battery. For this reason the battery charger converter and charging method, will be chosen based on battery technology and required life time. Among the various methods available for battery charging, constant current, constant voltage charging, hybrid method (constant voltage, constant current), pulse charging method and reflex charging method are well known. In this thesis, reflex charging method is studied since this method improves battery performance and extends battery life. In this method, the charger circuit, is composed of a bidirectional converter that transfers energy in both directions and between two sources. According to the specifications of the battery and power supply, type and structure of bidirectional converter for charger are chosen. In this thesis, two bidirectional converters, based on Buck-Flyback and Buck-Forward converters are proposed. In order to achieve higher power density and fast transient response, the circuit must operate at high switching frequencies. The proposed circuits are designed and implemented at high switching frequency. By increasing switching frequency, switching losses and electromagnetic interference increase. According to this issue, in two proposed converters, soft switching techniques are applied. Thus, converter switch in charging circuit turns on under ZVS condition. Also the converter applied in discharge circuit is soft switched. In this way, the proposed converters can implement, reflex charging with high efficiency. In this thesis, first a brief review of the battery types, several existing charging method and structures of presented converters for battery chargers, including proper unidirectional and bidirectional converters are presented. Then two bidirectional converters for implementing reflex charge method are presented. The proposed converters are analyzed. Also experimental results from laboratory prototype are presented. Keywords : Battery Charger, Bidirectional Converter, Reflex Charge, Soft Switching.
